Robbie Keane would not be many people's idea of a messiah, but to Celtic supporters buffeted by disappointment throughout a trying season selectivity is an unaffordable luxury. The words of the great American economist JK Galbraith came to life last Monday, when thousands disdained the freezing weather to travel to Celtic Park to welcome the striker as the time approached midnight.

"Desperate men are easily persuaded," Galbraith wrote, "because they wish desperately to be persuaded." Those suffering fans were incontestably touched by desperation, recent setbacks such as a draw and a defeat at home to Falkirk and Hibernian leaving Tony Mowbray's seemingly hapless squad 10 points behind Rangers.

Less than 24 hours after Keane's arrival the sense of desolation deepened when the Republic of Ireland striker's debut was marked by defeat at Kilmarnock. It is a fixture which Celtic teams of the past few years have tended to win unchallenged. This latest reversal amounted to another accretion of confirmation that, whatever managerial skills he may possess, Mowbray is not blessed with the fortune of the natural winner.

The consequence of the 11 defeats Celtic have sustained in his care so far this season was to be found in the irrational behaviour that accompanied the acquisition of a Tottenham reserve on loan until the end of the season. This manifestation of the urgent need to acclaim a redeemer would have caused any disinterested observer to believe that Lionel Messi had relocated to Glasgow.

Even such glee can sour almost overnight, however, and it is legitimate to suggest that, if Celtic are eliminated from the Scottish Cup at Dunfermline this afternoon, his future in his present position will be seriously threatened.

Supporters are aware that Mowbray's wins-to-matches ratio is already worse than that of the greatly discredited John Barnes in 1998-99; they are also cognisant of the fact that Barnes was sacked the day after a Scottish Cup defeat by Inverness Caledonian Thistle, the highland club then, like Dunfermline now, in the First Division.

The majority of those disenchanted supporters will see no difference between Barnes then and Mowbray now, although a substantial number will be prepared to argue that the latter's failings are even more pronounced. This claim is rooted in the conviction that the present Rangers side are emphatically more mediocre than Dick Advocaat's team were 11 years ago and that to be 10 points adrift of such opponents is scandalous.

There have been powerful hints that Mowbray was not the prime mover behind the Keane move, but that the directors, under the powerful influence of Dermot Desmond, persuaded themselves it would be worth meeting his earnings of around £65,000 a week. This is an eyebrow-raising departure from the club's long-practised policy of financial prudence and a measure of the directors' own desperation to sign a player who could make a telling difference.

In that sense, the board could not be said to have trusted Mowbray with substantial funds. Even the numerous players he signed in January were, by and large, balanced by those who were moved out. These are trying times for Mowbray, severe enough to suggest that he may be ill-equipped to survive.